The emergence of small lightweight long-running lithium ion batteries has facilitated a market for notebook computers, cell phones, and other portable devices. Lithium ion battery technology is also increasingly used in cars, such as hybrid vehicles that run on electricity powered by such batteries and gasoline, and electric cars that run exclusively on electricity generated by such batteries. Battery technology continues to expand to other areas, such as data centers, manufacturing and industrial applications, where hybrid power management requires extended battery life. In such battery powered systems, battery management can be important, for example, to ensure proper performance of the battery system while maintaining energy economy and overall system performance. An intelligent battery management system can lengthen battery life, reducing the system cost over its entire lifetime. The battery management system controls the functionality and charge of the battery cells. As the cells age, the storage capacity of the individual battery cells may lessen. The battery management system optimizes cell utilization considering the battery cell performance and battery life.